GB2042121A

GB2042121A - Tensioning device for chains

Info

Publication number: GB2042121A
Application number: GB7944251A
Authority: GB
Original assignee: Eisen und Drahtwerk Erlau AG
Current assignee: Erlau AG
Priority date: 1978-12-23
Filing date: 1979-12-21
Publication date: 1980-09-17
Also published as: US4456233A; BR7908470A; AT372507B; SE7910558L; GB2042121B; SE441616B; JPS5597545A; ATA791479A; DE2855989C2; YU299279A; IT1193251B; DE2855989A1; IT7928055A0

Description

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GB 2 042 121 A

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SPECIFICATION Tensioning device for chains

5 The invention relates to a tensioning device for chains, such as retaining chains, sling chains, tyre chains and the like, with a tensioning unit which comprises at least one tensioning spindle, which is connected by a screwthread to a tensioning nut and 10 with at least one damping spring.

In a known tensioning device of this type, the damping spring is located in the region close to the tensioning unit of the chain and is formed by a coil spring. Consequently, the tensioning device cannot 15 be used in short chains and high forces cannot be absorbed in the case of short anchoring distances.

It is the object of the invention to construct a tensioning device of this type so that on the one hand it has only a short length, but on the other 20 hand, it can absorb high forces.

This object is fulfilled according to the invention due to the fact that the damping spring is a pile of cup springs and that the pile of cup springs is located in the tensioning unit.

25 As a result of the use of cup springs as the damping spring, the tensioning device according to the invention may have a very short construction, which is able to absorb very high forces according to the arrangement and construction of the individual 30 cup springs of the pile. Since the pile of cup springs is located inside the tensioning unit, the length of the tensioning device is determined solely by the length of the tensioning unit. Since the pile of cup springs is only short, the tensioning unit can be kept extremely 35 short. The tensioning device is thus particularly suitable for use in short chains, where short anchoring distances are necessary in the case of high forces.

This tensioning device is all the more suitable for 40 chains of this type, since it is only narrow.

Further features of the invention will become apparent from the description, claims and drawings.

The invention is described in detail with reference to further embodiments illustrated in the drawings: 45 Figure 1 shows a first embodiment of a tensioning device according to the invention, in longitudinal section,

Figure 2 shows a second embodiment of a tensioning device according to the invention, in longitu-50 dinal section,

Figure 3 shows the tensioning device according to Figure 2 in elevation.

The tensioning device according to Figure 1 comprises two tensioning spindles 1,1', which are 55 inter-connected by a tensioning nut 2. The tensioning spindles 1,1' are constructed in the form of bolts and at one end support a plate 3,3'. The plates 3,3' are connected in a non-rotary manner to the tensioning spindle, they are preferably welded thereto. Over 60 more than half their length, the two tensioning spindles 1,1' comprise an external screwthread 5,5', which extends as far as the end of the tensioning spindle remote from the plate 3,3'. Guided on the part of the tensioning spindle comprising the exter-65 nal screwthread 5,5' is the tensioning nut 2 constructed as a sleeve, with the interposition of a terminal threaded bush 6,6' respectively, which are preferably soldered in the tensioning nut 2. The two tensioning spindles have a left and right-hand thread 70 respectively, which may be constructed as a V thread or trapezoidal thread. By rotating the tensioning nut 2 by means of a lever 7, the two tensioning spindles 1,1' are moved in opposite directions, due to which the chain which is not shown is shortened or 75 lengthened.

The two threaded bushes 6,6' of the tensioning nut 2 are respectively so long that the tensile forces applied can be absorbed without damaging in the inter-meshing threads. Since the tensioning nut has 80 a larger internal diameter than the threaded bushes 6 and 6', the part of the tensioning spindles 1,1' located inside the tensioning nut is at a distance from the inner wall of this remaining part of the tensioning nut, so that trouble-free tensioning of the 85 chain is ensured.

In the region of its end remote from the plate 3,3', each tensioning spindle comprises a pin 10,10' extending diametrically, both ends of which project respectively beyond the associated tensioning spin-90 die and serve as a stop for the threaded bushes 6 and 6', so that the tensioning spindles cannot be screwed out completely.

In order that the tensioning device and not the chain or hook or locks of the chain is able to absorb 95 forces, acting in a jerky manner on the chain, which forces may occur for example at the time of sudden deceleration or rapid acceleration, without damage, two damping springs 11,11' are provided. The latter are formed respectively by a pile of cup springs and 100 form part of the tensioning unit 12, consisting of tensioning spindles and tensioning nut. One thus dispenses not solely with the additional length required for damping springs in known tensioning devices, but in comparison with helical compression 105 springs or springs in the form of a truncated cone, even higher forces can be observed, whilst simultaneously reducing the outer diameter of the tensioning device. The tensioning device is therefore relatively short and narrow, so that it is suitable for 110 use in short chains. In order to achieve a simple construction, the piles of springs 11,11'are disposed around the tensioning spindles 1, and I'.The piles of springs cannot be overloaded in operation. Furthermore, with the latter, the tensioning displace-115 ment of the tensioning device can be pre-determined accurately in an advantageous manner. In order to be able to vary the magnitude of the force to be absorbed according to the applications of the tensioning device provided, the piles of springs may be 120 constructed so that the individual cup springs are arranged in one or more layers and are disposed in the same direction or alternate directions. However, it is also possible to use piles which are arranged in rows in alternate directions as damping springs. In 125 Figures 1 and 2, the piles of springs are illustrated respectively by cup springs, 26 of which are provided, arranged in rows in alternate directions,

which have a spring deflection of 19.5mm. For example, 50% of the springs may be disposed in one 130 layer, 25% in two layers and the remaining 25% in

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three layers. This increases the pre-tensioning force with an increasing tensioning distance, so that the tensioning device is not stressed as a block formation. In another more suitable arrangement of the 5 springs in the pile of springs 11,11', by way of example, 80% of the total spring deflection are pre-tensioned with a force of 800kp, whereas the remaining 20% of the spring deflection are pre-tensioned at 1600kp, for which purpose the cup 10 springs or piles of cup springs have a varying load capacity, which is achieved due to the fact that either cup springs of varying thickness or piles of cup springs of identical individual springs arranged in layers of different numbers are provided. 15 For protection against dirt and damage, the piles of springs 11,11' are appropriately located in a tubular housing 13,13'. Consequentlyatensioning device can even be used under severe operating conditions, without impairing its operational reliabil-20 ity. Apart from the piles of springs 11,11', the housings 13 and 13' also surround the associated tensioning spingle 1,1' and with the shortest length of the tensioning device (right-hand side of Figure 1), i.e. with maximum tensioning of the chain, extend 25 over approximately three quarters of the associated half of the tensioning nut 2. The tensioning spindles 1 and 1' are thus protected to a high degree from damage and dirt and very reliable guidance is ensured when the tensioning spindles 1, V are 30 displaced in the tensioning nut 2.

The housings 13,13' also serve for securing the position of the piles of springs 11 and 11' and prevent the piles of springs from being able to bend over their length. The spring force thus always acts 35 exactly in the longitudinal direction of the tensioning device, so that the piles of springs are able to absorb the full pre-determined force. The piles of springs 11, 11' are located with a small clearance inside the housings 13 and 13' and with slight clearance on the 40 associated tensioning spindles 1 and 1', so that during tensioning, they do not become caught on the inner wall of the housing or on the outer side of the spindle and can be untensioned without hindrance. The piles of springs are supported at one end 45 on one end wall 14,14' of the housings 13,13' which wall serves as an outer support and at their other end on the plates 3,3' on the tensioning spindles 1, 1', which plates serve as an abutment. As a result of this arrangement and position of the abutments 3,3' 50 and outersupports 14,14', the overall length of the tensioning device is reduced further without impairing the possible tensioning travel. The construction of the abutment 3,3' asa plate ensures that the piles of springs are supported over a large surface area. 55 Likewise, the piles of springs can be supported in a trouble-free manner on the end wall 14,14' of the housing.

In orderto prevent rotation of the tensioning spindles 1,1'inside the housing 13,13', the plate 3, 60 3' is mounted in a non-rotary manner in the housing. Preventing the rotation of the plate 3,3' is ensured by bolts 15,15', which are respectively mounted in a stationary manner in one of the end walls 3,3' and project by one end 16,16' at right-angles to the 65 longitudinal axis of the tensioning device, through the walls 3 and 3'. It is essential to the invention that these ends 16 and 16' project respectively into associated longitudinal slots 17 and 17' in the housings 3 and 3', because due to this the bolts 15 and 15' serve not only for preventing rotation of the tensioning spindles 1 and 1', but also as indicators for the load on the chain. This is particularly advantageous in the case of short chains, where high forces may easily lead to excessive loading of the chain and its accessories. Damage to the chain and adjoining parts may thus be easily avoided.

The length ofthe longitudinal slots 17 and 17' is selected so that it corresponds to the entire tensioning region. The latter is characterised by markings (not shown) at the ends ofthe slots. Furthermore, the free ends 16,16' ofthe bolts 15,15' are marked in colour to facilitate rapid reading ofthe respective force.

The tensioning spindles project respectively through central openings 18 and 18' in the end walls 14 and 14'. Between these openings 18 and 18', the tensioning spindles 1 and 1' are slidably guided by way of the threaded bushes 6 and 6' in the tensioning nut 2. In the untensioned position ofthe tensioning device (left-hand side of Figure 1), the tensioning nut 2 projects by its ends 9 and 9' into the housings 13 and 13' to such an extent that the threaded bushes 6 and 6' are located inside the housing. The threaded bushes 6 and 6' are located in a tapered section 12,12' ofthe housing, which is attached, namely welded to the corresponding end walls 14,14'. Preferably, the end faces 14 and 14' each have an axially extending collar 4,4', which projects in a form-hugging manner into the sections 12,12' ofthe housing. In the embodiment according to Figure 1, the end walls 14 and 14' are respectively separate parts, which are also welded to the outer enlarged sections 8 and 8' ofthe housing.

Asa result ofthe arrangement ofthe housing 13, 13' and the construction of the tensioning nut 2 as a sleeve, the section ofthe tensioning spindles 1 and 1' comprising the external screwthread 5,5' is located in the housing, protected over its entire length and in the tensioning nut, so that the screwthreads ofthe tensioning spindle cannot be contaminated. Due to this, the tensioning device also ensures trouble-free tensioning after it has been in use for a long period of time. The length ofthe housing 13 and 13' measured in the axial direction of the tensioning spindle is naturally so great that the maximum tensioning length determined by the length ofthe section ofthe tensioning spindle comprising the external screwthread 5,5' can be utilised. When the tensioning nut projects by its ends 9 and 9' into the housing 13 and 13', forces which possibly occur and act at right-angles to the axis of the tensioning nut 2, may also be absorbed by the housing, so that the tensioning spindles 1 and 1' are only subjected to slight bending stress.

Attached to the axially outer end faces ofthe housings 13 and 13' is a fork-like connecting part 19, 19', which in its two limbs 20,21 respectively 20', 21' comprise aligning apertures for bearing bolts 22 and 22'. Suspended in the bearing bolts 22 and 22' are end members 24 and 24' of an associated strand of

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chain (not shown). For securing the position ofthe bearing bolts 22 and 22', each limb is respectively provided with an aperture for a securing pin 25,26, 25', 26', which aperture extends at right-angles to 5 the longitudinal axis ofthe bearing bolt and between which securing pins the associated bearing bolt is secured axially.

The connecting parts 19 and 19' with the bearing bolts 22 and 22' are preferably constructed so that 10 only a chain adjusted to the respective tensioning device as regards its breaking strength can be suspended from the latter. In order to exchange the chain or tensioning device, the bearing bolts 22 and 22' can be released from the connecting parts 19 and 15 19'.

Mounted halfway along the tensioning nut 2 is the tensioning lever 7, which projects through two diametrically opposed openings 27 and 27' in the tensioning nut 2. The tensioning lever 7 has a 20 straight construction and is mounted to slide in the tensioning nut 2. In order to prevent the tensioning lever 7 from sliding through the tensioning nut, at both its ends the tensioning lever comprises a stop 28 and 28', which consists of a ring surrounding the 25 end 29,29' of reduced diameter ofthe tensioning lever, the outer diameter of which ring is greater than the diameter ofthe openings 27,27'. At the time of clamping, in order to prevent the material to be clamped, in particular sheet metal containers, from 30 being damaged by the rings 28 and 28', a further ring 30 and 30', which is resilient across its diameter and preferably consists of rubber is provided on the inner faces 23 and 23' which are in facing relationship.

35 The tensioning lever 7 is mounted on the tensioning nut 2 so that when they are completely inserted in the housings 13 and 13', the tensioning spindles 1 and 1' are still at a distance from the section ofthe lever located inside the tensioning nut 2 or at the 40 most bear against the latter.

Fortensioning the chain 8, the tensioning nut 2 is rotated by the lever 7 about its axis so that the two tensioning spindles 1 and 1' are moved towards each other. As a result ofthe fact that this position is 45 secured by the bolts 15 and 15' engaging in the plates 3 and 3', the tensioning spindles 1 and 1' and the housings 13 and 13' are prevented from rotating so that the strands of chain suspended in the connecting parts 19 and 19' are not rotated. The 50 plates3and3' bear undertheforce of the piles of springs 11 and 11' against the connecting parts 19 and 19'. The force of the pile of springs is so high that at the time of tensioning, the traction exerted by the two strands of chain on the housings 13 and 13' 55 is less than the force necessary for compressing the piles of springs. Thus, when the two tensioning spindles 1 and 1' are moved towards each other, the housings 13 and 13' bear against the plates 3 and 3'. The spring force is selected so that the strands of 60 chain can be tensioned sufficiently by the tensioning device. For untensioning, it is solely necessary to rotate the tensioning lever 7 in the opposite direction, in which case the two tensioning spindles 1 and 1' are moved away from each other as a result of the 65 inter-meshing threads of the threaded bolts 6 and 6'

and tensioning spindles 1 and 1'. At the time of untensioning, the end position is reached when the pins 10 and 10' in the regions ofthe ends ofthe tensioning spindles come to bear against the 70 threaded bolts 6 and 6'. Maximum tension is achieved when the ends ofthe tensioning spindles come to bear against the tensioning lever 7 (Figure 1 right-hand half). Now, if high forces come to act in a jerky manner, such as for example at the time of 75 rapid deceleration, then the housings 13 and 13' are displaced with respect to the tensioning spindles 1 and 1' against the force ofthe piles of springs 11 and 11', in which case the bolts 15 and 15' slide in the longitudinal slots 17 and 17' in the housings 13 and 80 13'. The piles of springs absorb these high forces and thus protect the entire tensioning device from damage or fracture. Directly after the force subsides, the piles of springs push the plates 3 and 3' back against the end walls 16 and 16' ofthe housing. In 85 the embodiment, the greater length L-i ofthe tensioning device amounts to 492mm plus a spring deflection of twice 19.5mm and the smallest length L-2 amounts to 396mm plus a spring displacement of twice 8mm.

90 In the embodiment according to Figures 2 and 3, only one pile of springs 11a is provided consisting of cup springs of partly varying thickness arranged in rows in opposite directions. The pile of springs 11a, which is seated on a rod 1 a corresponding to the 95 spindle, is disposed in a housing 13a. At one end, the latter supports one connecting part 19a, which is preferably welded to the associated end faces. The other connecting part 19 is welded to the free end 24 ofthe rod 1a remote from the plate 3a. For this 100 purpose, the end 24 projects into a corresponding opening in the connecting part 19a.

Otherwise, the connecting parts are constructed according to the embodiment of Figure 1.

Indication ofthe load and prevention of rotation 105 are once more carried out by the bolt 15a, which projects through the plate 3a and is slidably guided in a slot 17a in the housing 13a. In contrast to the aforedescribed housings, the housing 13a has the same outer and inner diameter over its entire length, 110 so that in the untensioned position ofthe tensioning device, the end wall 14a remote from the plate 3a forms a stop for the connecting part 19a (Figure 2).

As in the tensioning device according to Figure 1, the longitudinal slot 17a is located approximately in 115 the axially outerthird ofthe housing 13a and terminates at solely a small distance from the connecting part 19a.

Since, in place of the two tensioning spindles according to Figure 1, only one rod 1a is provided, 120 no tensioning nut is provided for connecting the tensioning spindles. The tensioning device according to Figures 2 and 3 is self-tensioning, since the rod 1a is moved undertheforce ofthe pile of springs 11a into the housing 13a as soon as the chain or chains 125 become slack or when jerky forces occur. The latter can be absorbed in a trouble-free manner by the . single pile of springs 11a, in that a relative movement between the housing 13a and the rod 1a mounted in the housing takes place, in which case 130 the pile of springs 11a is tensioned. In this embodi

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ment, several piles of springs may also be provided, so that the tensioning device can absorb a high tensioning force and thus high forces without danger of damage to or destruction of the tensioning

5 device.

In the retracted position ofthe rod 1a, the device has a length L of preferably 208.5mm. The maximum damping force amounts to 8.21 with a maximum spring deflection of 40.5mm.

10 The tensioning device is suitable for retaining chains, sling chains, towing chains, tyre protection chains, anti-skid tyre chains and above all for clamping chains.

Claims

15 CLAIMS

1. Tensioning device for chains, such as retaining chains, sling chains, tyre chains and the like, with a tensioning unit which comprises at least one

20 tensioning spindle and with at least one damping spring, characterised in that the damping spring is a pile of cup springs and that the pile of cup springs is located in the tensioning unit.

2. Tensioning device according to claim 1, char-

25 acterised in that the cup springs ofthe pile of springs each have the same construction.

3. Tensioning device according to claim 1 or 2, characterised in that the cup springs are disposed in alternate directions.

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4. Tensioning device according to claim 3, characterised in that a plurality of cup springs are disposed in one layer and the remaining cup springs are disposed in several other layers.

5. Tensioning device according to claim 4, char-

35 acterised in that the cup springs disposed in several layers form layers with a differing number of springs.

6. Tensioning device according to one of claims 3 to 5, characterised in that approximately half of the

40 cup springs are disposed in one layer and approximately the other half are disposed in a plurality of layer comprising a differing number, approximately 28% ofthe other half preferably being disposed in two layers and approximately 25% in three layers.

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7. Tensioning device according to one of claims 1 to 6, characterised in that more than half the spring deflection, preferably approximately 80% ofthe total spring deflection ofthe pile of springs is pre-tensioned by half the force, which is at least

50 approximately half ofthe pre-tensioning force ofthe remaining spring deflection.

8. Tensioning device according to one of claims 1 to 7 characterised in that a plurality of piles of cup springs each preferably having a different number of

55 layers, are provided.

9. Tensioning device according to one of claims 1 to 8, characterised in that a monitoring device is provided for the respective pre-tensioning force of the pile of cup springs.

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10. Tensioning device according to claim 9, characterised in that the monitoring device supports an indicator connected to the tensioning spindle which indicator is able to slide longitudinally in an aperture in the housing.

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11. Tensioning device according to claim 10

characterised in that the indicator is located approximately radially with respect to the tensioning spindle and is attached to a terminal stop and projects by its protruding end into the opening in the housing.

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12. Tensioning device according to any preceding claim wherein the tensioning spindle is connected by a screwthread to a tensioning nut.

13. Tensioning device according to claim 12 comprising two tensioning spindles having oppo-

75 sitely handed screw threads and cooperating with a common tensioning nut.

14. Tensioning device substantially as hereinbefore described with reference to and as illustrated in Figure 1 or Figures 2 and 3 ofthe accompanying

80 drawings.

Printed for Her Majesty's Stationery Office by Croydon Printing Company Limited, Croydon Surrey, 1980.

Published by the Patent Office, 25 Southampton Buiidings, London, WC2A1 AY, from which copies may be obtained.